Bill Cosby -- Gun Fears at Concert Venue

Bill Cosby has reason to worry about his security ... so much so one of the venues where he was scheduled to perform imposed a mandatory gun check on the audience.

The Tarrytown Music Hall in N.Y. was preparing for a Cosby concert this Saturday, the prep included a significant weapons security check, which includes:

-- Metal detector wands at the door
-- No firearms, knives or other weapons
-- No backpacks

The theater also made it clear ... there would be zero tolerance for any protests inside the venue.

The Exec Director of the theater tells TMZ the extra security measures were not routine ... they were rolled out for Cosby's show.